Study on the Optimization of Biogas Production from Cow Dung and Wheat Straw Wastes through Co-digested Process

Abstract

Biogas is renewable energy carrier produced by anaerobic digestion of organic substrates and is considered a Sustainable alternative to fossil based fuels. This study focused on optimizing the production of biogas by co-digesting cow dung and wheat straw wastes. In this study, production of biogas from wheat straw (WS) and cow dung (CD) via co-digestion process was evaluated under mesophilic conditions using a batch digester for 35 days; which had high methane gas under optimum temperature, pH, and substrate mix ratio. In all treatments, physicochemical parameters such as total solid, volatile solid, moisture content, carbon to nitrogen ratio, and pH were measured before and after digestion. The experiment for biogas production by wheat straw and cow dung wastes was conducted using response surface methodology. Three numeric factors and three- levels Box-Behnken design expert was employed to study the effect of wheat straw to cow dung mix ratio, pH, and temperature for produced biogas yield. A total of 17 runs with replicates were performed. Gas production was noticed in all of the digesters starting from day 4th of anaerobic digestion. The daily biogas production was subsequently measured by gas syringe for 35 days and the methane gas composition was also analyzed by a gas analyzer. Cumulative biogas production revealed that substrate in a mix ratio of 75% WS +25% CD at pH of 7.0, and at temperature of 37.5℃ showed the highest cumulative volume of biogas production (198mL), and composition of methane gas (62.5%) as an optimal condition. Further researches have to be done to improve the production of high quality and quantity of production of biogas